The polar bear was 25 years old

According to zoo officials, the 25-year-old polar bear, named Anton, became sick and started to vomit up pieces of fabric. Zoo keepers don’t know why Anton ate the object, but they suspect it might have had some sort of food in it that the polar bear wanted. Anton died on Monday after suffering from severe intestinal injuries, reports the Associated Press.

The Wilhelma Zoo has asked that visitors alert an official if anything is dropped into an animal’s area so that it can be removed quickly, the Associated Press notes.

“If we had known that something was in the enclosure we might have been able to save Anton,” Tobias Knauf-Witzens, a vet, told The Daily Express.

This isn’t the first time the zoo has lost an animal because something was dropped in its area. An elephant seal housed at the zoo died after eating a small toy and a hippo died after eating a tennis ball, The Daily Express notes.